/// <summary>
/// Queries the local Consul agent for healthy instances of a given service and selects one such instance.
/// </summary>
/// <param name="query">Query used to find services instances.</param>
/// <exception cref="NoAvailableServiceInstanceException">Thrown when there is no healthy instance available for that service.</exception>
/// <returns>Returns a service instance.</returns>
public ServiceInstanceDescriptor GetServiceInstance(ServiceInstanceQuery query, ServiceInstanceSelectionStrategy?strategy = null)
{
IServiceInstanceSelectionStrategy selectionStrategy = null;
if (strategy.HasValue)
{
selectionStrategy = InitializeServiceInstanceSelectionStrategy(strategy.Value);
}
else
{
selectionStrategy = DefaultServiceInstanceSelectionStrategy;
}
if (selectionStrategy == null)
{
throw new MagellanException("Could not initialize any service instance selection strategy.");
}
//Query for available instances
ICollection <ServiceInstanceDescriptor> availableInstances = GetServiceInstances(query);
//Select instance
if (availableInstances.Count > 0)
{
return(selectionStrategy.SelectServiceInstance(availableInstances));
}
else
{
throw new NoAvailableServiceInstanceException();
}
}
/// <summary>
/// Sets up the Magellan client with all needed configuration options.
/// </summary>
/// <param name="configuration">The configuration for the Magellan client.</param>
public MagellanClient(MagellanClientConfiguration configuration)
{
//Set default service selection strategy
DefaultServiceInstanceSelectionStrategy = InitializeServiceInstanceSelectionStrategy(configuration.DefaultServiceInstanceSelectionStrategy);
//Initialize Consul client
Consul = new ConsulClient(consulClientConfig =>
{
consulClientConfig.Address = new Uri($"http://{configuration.ConsulAgentHost}:{configuration.ConsulAgentPort.ToString()}");
});
}
/// <summary>
/// Initializes a service instance selection strategy object.
/// </summary>
/// <param name="strategyType">Type of strategy to initialize an object for.</param>
/// <returns>Returns a service selection strategy.</returns>
private IServiceInstanceSelectionStrategy InitializeServiceInstanceSelectionStrategy(ServiceInstanceSelectionStrategy strategyType)
{
IServiceInstanceSelectionStrategy strategy = null;
switch (strategyType)
{
case ServiceInstanceSelectionStrategy.RandomServiceInstanceSelection:
strategy = new RandomServiceInstanceSelectionStrategy();
break;
default:
throw new NotImplementedException($"No implementation available for service instance selection strategy {strategyType}.");
}
return(strategy);
}
